Delocalized electron
In physics delocalized electrons are
electrons in a
molecule that are not associated with a single
atom or a
covalent bond. Delocalized electrons are part of a
pi electron system that extends over several adjacent atoms. Delocalized electrons can be found in
conjugated systems of
double bonds and in
aromatic and mesoionic systems. A case of delocalized electrons occurs also in solid
metals, where the
d-subshell interferes with the above
s-subshell, and contributes to the properties of a metal.
In the
simple aromatic ring benzene the delocalization of six pi electrons over the whole ring is often graphically indicated by a circle.
Encyclopedia
In physics
delocalized electrons are
electrons in a
molecule that are not associated with a single
atom or a
covalent bond. Delocalized electrons are part of a
pi electron system that extends over several adjacent atoms. Delocalized electrons can be found in
conjugated systems of
double bonds and in
aromatic and mesoionic systems. A case of delocalized electrons occurs also in solid
metals, where the
d-subshell interferes with the above
s-subshell, and contributes to the properties of a metal.
In the
simple aromatic ring benzene the
delocalization of six pi electrons over the whole ring is often graphically indicated by a circle. This shows that the its bond lengths are equal for all the C-C bonds.Alternatively, benzene can be represented by
resonance structures.
Another example of a delocalized electrons can be found in a
carboxylic acid. When dissolved in an aqueous solution, the hydroxyl group releases a proton and the electrons are then delocalized between the two oxygen atoms in the carboxylate anion.
Delocalized electrons are important for several reasons. One, an expected chemical reaction may not occur because the electrons delocalize to a more stable configuration, resulting in a reaction that happens at a different location. An example attempting the Fridel-Crafts alkylation of benzene with 1-chloro-2-methylpropane; the
carbocation rearranges to a tert-butyl group stabilized by hyperconjugation, a particular form of delocalization.
Delocalized electrons also exist in the structure of
metals. Metallic structure consist of aligned positive ions in a "sea" of delocalized electrons. This means that the electrons are free to move throughout the structure, and gives rise to properties such as conductivity.
See also resonance .
